Caller identification (caller ID) was created to alert a called party of the originating source of an incoming call. This way, the called party is able to make an informed decision about whether or not to accept the incoming call. However, caller ID spoofing has been used to trick a called party into thinking the source of an incoming call is different than the actual source. For example, the caller may spoof their number to make the called party think a neighbor is calling. This has been used to subject called parties to scams, spammers, or even swatting attacks.
To combat caller ID spoofing, secure telephony identity revisited (STIR) and secure handling of asserted information using tokens (SHAKEN) were developed. SHAKEN/STIR use cryptographic identity headers to provide confirmation of identity to a called party. The identity headers are passed to the called party with the call itself, which requires the call to be carried out end-to-end on an Internet Protocol (IP) network. However, some calls are still routed through the public switched telephone network (PSTN), for example, which strips the call of extra fields, removing the ability for the called party to authenticate the call using SHAKEN/STIR.